Two new borates containing the first examples of large isolated polyborate anions: chain [B7O9(OH)5]2- and ring [B14O20(OH)6]4-.

Two novel hydrated borates were synthesized under mild solvothermal conditions. One is hydrated rubidium borate, Rb2B7O9(OH)5, which contains the first example of the isolated chain heptaborate anion, [B7O9(OH)5]2-. The other is hydrated diethylenetriamine borate, [(C4H15N3)]2[B14O20(OH)6], which contains the first example of the largest isolated ring tetradecaborate anion, [B14O20(OH)6]4-.